This addresses a bug where users initialize empty sortable lists are
add items dynamically. In this situation refresh() should recognize the
position and orientation of the new items.
Fixes #7498
Closesgh-1381

Selectmenu's test suite broke with b0e8380, which changed the padding
used by the menu widget. Selectmenu conditionally adds pixels to the
menu's width, and using closeEnough() accounts for that and the
rounding differences across browsers.
Closesgh-1275